U.S. patent application number 13/818817 was filed with the patent office on 2014-07-24 for position estimation device, position estimation method, program, and integrated circuit.
The applicant listed for this patent is Panasonic Corporation. Invention is credited to Mitsuaki Oshima, Kazunori Yamada.
Application Number | 20140206381 13/818817 |
Document ID | / |
Family ID | 48191622 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140206381 |
Kind Code |
A1 |
Yamada; Kazunori ; et
al. |
July 24, 2014 |
POSITION ESTIMATION DEVICE, POSITION ESTIMATION METHOD, PROGRAM,
AND INTEGRATED CIRCUIT
Abstract
A position estimation device including: a provisional position
setting unit which sets current position information indicating an
estimated current position of a wireless terminal; a distance
estimation unit which estimates, using receiving strengths of
signals received from plural wireless stations, distance
information indicating distances from the plural wireless stations
to the wireless terminal; a possible area calculation unit which
calculates, using the distance information and map information
indicating a spatial structure, an area in the spatial structure
which can maintain the distances indicated in the distance
information, as a possible area in the spatial structure in which
the wireless terminal is likely to be present; and a correction
unit which corrects the current position indicated in the current
position information to a position within the possible area when
the current position is outside the possible area.
Inventors: |
Yamada; Kazunori; (Hyogo,
JP) ; Oshima; Mitsuaki; (Kyoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Corporation |
Kadoma-shi, Osaka |
|
JP |
|
|
Family ID: |
48191622 |
Appl. No.: |
13/818817 |
Filed: |
October 12, 2012 |
PCT Filed: |
October 12, 2012 |
PCT NO: |
PCT/JP2012/006553 |
371 Date: |
February 25, 2013 |
Current U.S.
Class: |
455/456.1 |
Current CPC
Class: |
G01S 5/14 20130101; G01S
5/10 20130101; H04W 52/0245 20130101; Y02D 70/142 20180101; H04W
52/0251 20130101; G01S 5/0263 20130101; H04W 4/33 20180201; Y02D
30/70 20200801 |
Class at
Publication: |
455/456.1 |
International
Class: |
G01S 5/10 20060101
G01S005/10; H04W 4/04 20060101 H04W004/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2011 |
JP |
2011-238149 |
Claims
1. A position estimation device comprising: a setting unit
configured to set current position information indicating an
estimated current position of a wireless terminal; an estimation
unit configured to estimate, using receiving strengths of signals
received from plural wireless stations including at least a mobile
station, distance information indicating distances from the plural
wireless stations to the wireless terminal; a calculation unit
configured to calculate, using the distance information and map
information indicating a spatial structure, an area in the spatial
structure in which the wireless terminal satisfies the distances
indicated in the distance information, as a possible area in the
spatial structure in which the wireless terminal is likely to be
present, the spatial structure including at least a layout of a
building; and a correction unit configured to correct the current
position indicated in the current position information to a
position within the possible area when the current position is
outside the possible area.
2. The position estimation device according to claim 1, wherein the
position estimation device is in the wireless terminal.
3. The position estimation device according to claim 1, wherein the
spatial structure indicated in the map information includes the
layout of the building and a position, in the building, of an
obstacle which attenuates a signal, and when the obstacle is
present in the spatial structure in a first distance indicated in
the distance information, the calculation unit is configured to
calculate the possible area using a second distance which is
obtained by correcting the first distance according to the
obstacle.
4. The position estimation device according to claim 1, further
comprising an instruction unit configured to instruct wireless
stations which, among the plural wireless stations, belong to a
same network to change a communication mode, wherein the estimation
unit is configured to measure receiving strengths of signals
transmitted by the wireless stations which have changed the
communication mode in response to the instruction, and estimate the
distance information using the measured receiving strengths.
5. The position estimation device according to claim 1, further
comprising an obtaining unit configured to communicate with each of
the plural wireless stations and obtain wireless station
information held by each of the plural wireless stations, wherein
the calculation unit is configured to calculate the possible area
using the map information, the distance information, and the
wireless station information.
6. The position estimation device according to claim 5, wherein the
wireless stations include a mobile station and a fixed station, and
the wireless station information, when held by one of the wireless
stations which is the fixed station, includes position information
indicating a position of the fixed station.
7. The position estimation device according to claim 5, wherein the
wireless station information includes distance information
indicating a distance between one of the wireless stations which
holds the wireless station information and a different one of the
wireless stations.
8. The position estimation device according to claim 5, wherein the
wireless station information includes a transmitting strength of a
signal transmitted by the wireless station holding the wireless
station information, and the estimation unit is configured to
estimate the distance information using the receiving strengths and
the transmitting strength.
9. The position estimation device according to claim 1, further
comprising a detection unit configured to detect acceleration
information on the wireless terminal and direction information on
the wireless terminal, wherein the setting unit is configured to
set, as the current position information, a current position
estimated by autonomous navigation using the acceleration
information and the direction information detected by the detection
unit.
10. The position estimation device according to claim 1, wherein
the estimation unit is configured to estimate, using a receiving
strength of a signal received from a base station included in the
plural wireless stations, distance information indicating a
distance from the base station to the wireless terminal, and the
setting unit is configured to set, as the current position
information, a position of the wireless terminal estimated using
the distance information indicating the distance from the base
station to the wireless terminal and position information on the
base station.
11. The position estimation device according to claim 1, further
comprising: a detection unit configured to detect acceleration
information on the wireless terminal and direction information on
the wireless terminal; and an autonomous navigation position
estimation unit configured to estimate the current position of the
wireless terminal by autonomous navigation using the acceleration
information and the direction information detected by the detection
unit, wherein the setting unit is configured to set, as the current
position information, the current position estimated by the
autonomous navigation position estimation unit.
12. The position estimation device according to claim 11, further
comprising a determination unit configured to determine whether or
not the current position information set by the setting unit needs
to be corrected, based on current position accuracy indicating
accuracy of the current position estimated by the autonomous
navigation position estimation unit, wherein the determination unit
is configured to determine that the current position information
needs to be corrected when the current position accuracy is lower
than or equal to a threshold, and the calculation unit is
configured to calculate the possible area only when the
determination unit determines that the current position information
needs to be corrected.
13. The position estimation device according to claim 12, wherein
the current position accuracy has a value which decreases with
increase in interval between a first time and a second time to
indicate a decrease in the accuracy of the current position, the
first time being a time at which the current position has been
estimated by the autonomous navigation position estimation unit and
the second time being a time at which a previous current position
before the current position has been estimated by the autonomous
navigation position estimation unit.
14. A position estimation method comprising: setting current
position information indicating an estimated current position of a
wireless terminal; estimating, using receiving strengths of signals
received from plural wireless stations including at least a mobile
station, distance information indicating distances from the plural
wireless stations to the wireless terminal; calculating, using the
distance information and map information indicating a spatial
structure, an area in the spatial structure in which the wireless
terminal satisfies the distances indicated in the distance
information, as a possible area in the spatial structure in which
the wireless terminal is likely to be present, the spatial
structure including at least a layout of a building; and correcting
the current position indicated in the current position information
to a position within the possible area when the current position is
outside the possible area.
15. A non-transitory computer-readable recording medium for use in
a computer, the recording medium having a computer program recorded
thereon for causing the computer to execute: setting current
position information indicating an estimated current position of a
wireless terminal; estimating, using receiving strengths of signals
received from plural wireless stations including at least a mobile
station, distance information indicating distances from the plural
wireless stations to the wireless terminal; calculating, using the
distance information and map information indicating a spatial
structure, an area in the spatial structure in which the wireless
terminal satisfies the distances indicated in the distance
information, as a possible area in the spatial structure in which
the wireless terminal is likely to be present, the spatial
structure including at least a layout of a building; and correcting
the current position indicated in the current position information
to a position within the possible area when the current position is
outside the possible area.
16. An integrated circuit which estimates a current position of a
wireless terminal, the integrated circuit comprising: a setting
unit configured to set current position information indicating the
current position of the wireless terminal; an estimation unit
configured to estimate, using receiving strengths of signals
received from plural wireless stations including at least a mobile
station, distance information indicating distances from the plural
wireless stations to the wireless terminal; a calculation unit
configured to calculate, using the distance information and map
information indicating a spatial structure, an area in the spatial
structure in which the wireless terminal satisfies the distances
indicated in the distance information, as a possible area in the
spatial structure in which the wireless terminal is likely to be
present, the spatial structure including at least a layout of a
building; and a correction unit configured to correct the current
position indicated in the current position information to a
position within the possible area when the current position is
outside the possible area.
Description
TECHNICAL FIELD
[0001] The present invention relates to a position estimation
device, a position estimation method, a program, and an integrated
circuit for estimating a current position of a wireless
terminal.
BACKGROUND ART
[0002] Recent years have seen a progress in the introduction of
Home Energy Management System (HEMS) which connects various home
appliances to a home network and controls the home appliances using
information technology (IT) in order to manage power consumption
considering environmental issues, for example.
[0003] The control performed by the HEMS includes turning on/off
the home appliances according to the position of a user of the
system, thereby requiring a high-accuracy indoor position
estimation technique.
[0004] An example of indoor position estimation techniques is to
estimate the position of a wireless terminal by calculating the
distance from a wireless station which performs wireless
communication, base on a property that the receiving strength of a
signal from the wireless station attenuates according to the
distance from the wireless station.
[0005] When there are few base stations whose positions are known
in advance, Patent Literature (PTL) 1 obtains position information
on a particular terminal by means of actual measurement and uses
that particular terminal as a base station to increase the accuracy
of the position estimation.
CITATION LIST
Patent Literature
[0006] [PTL 1] Japanese Unexamined Patent Application Publication
No. 2008-17027
SUMMARY OF INVENTION
Technical Problem
[0007] However, the above conventional method requires obtaining of
the position information on a particular terminal by some kind of
means of actual measurement, making it difficult to apply the
conventional method to a wireless terminal which is not equipped
with a means of actual measurement.
[0008] In view of the above problem, it is an object of the present
invention to provide a position estimation device which, when there
are few base stations whose positions are known in advance,
increases the accuracy of the position estimation without requiring
addition of a special positioning device.
Solution to Problem
[0009] To solve the above problem, the position estimation device
according to an aspect of the present invention includes: a setting
unit configured to set current position information indicating an
estimated current position of a wireless terminal; an estimation
unit configured to estimate, using receiving strengths of signals
received from plural wireless stations including at least a mobile
station, distance information indicating distances from the plural
wireless stations to the wireless terminal; a calculation unit
configured to calculate, using the distance information and map
information indicating a spatial structure, an area in the spatial
structure in which the wireless terminal satisfies the distances
indicated in the distance information, as a possible area in the
spatial structure in which the wireless terminal is likely to be
present, the spatial structure including at least a layout of a
building; and a correction unit configured to correct the current
position indicated in the current position information to a
position within the possible area when the current position is
outside the possible area.
[0010] It is to be noted that these general or specific aspects may
be realized using a system, a method, an integrated circuit, a
computer program, or a computer-readable recording medium such as a
CD-ROM, or any combination of systems, methods, integrated
circuits, computer programs, or recording media.
Advantageous Effects of Invention
[0011] A position estimation device according to an aspect of the
present invention increases the accuracy of the position estimation
without requiring addition of a special positioning device when
there are few base stations whose positions are known in
advance.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a block diagram showing a configuration of a
position estimation device according to Embodiment 1.
[0013] FIG. 2 is a diagram showing an example of base station
management information according to Embodiment 1.
[0014] FIG. 3 is a diagram showing a relationship between receiving
field strength and distance according to Embodiment 1.
[0015] FIG. 4 is a diagram showing a specific example of estimated
distance information and distance accuracy information according to
Embodiment 1.
[0016] FIG. 5 is a diagram showing map information and an example
of placement of wireless stations according to Embodiment 1.
[0017] FIG. 6 is a diagram showing an example of wireless station
information according to Embodiment 1.
[0018] FIG. 7 is a diagram showing an example of other wireless
station information according to Embodiment 1.
[0019] FIG. 8A is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0020] FIG. 8B is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0021] FIG. 9 is a diagram showing an example of association
between types of obstacle and correction scaling factors according
to Embodiment 1.
[0022] FIG. 10A is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0023] FIG. 10B is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0024] FIG. 11 is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0025] FIG. 12A is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0026] FIG. 12B is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0027] FIG. 12C is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0028] FIG. 13A is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0029] FIG. 13B is a diagram for describing a method of calculating
a possible area according to Embodiment 1.
[0030] FIG. 14 is a diagram showing a specific example of a
possible area calculated according to Embodiment 1.
[0031] FIG. 15 is a diagram showing a specific example of a
possible area calculated according to Embodiment 1.
[0032] FIG. 16 is a diagram showing a specific example of a
possible area calculated according to Embodiment 1.
[0033] FIG. 17 is a diagram showing a specific example of a
possible area calculated according to Embodiment 1.
[0034] FIG. 18 is a flowchart showing operations of a position
estimation device according to Embodiment 1.
[0035] FIG. 19 is a flowchart showing operations of a position
estimation device according to Embodiment 1.
[0036] FIG. 20 is a flowchart showing operations of a position
estimation device according to Embodiment 1.
[0037] FIG. 21 is a flowchart showing operations of a position
estimation device according to Embodiment 1.
[0038] FIG. 22 is a block diagram showing a minimum configuration
of a position estimation device.
[0039] FIG. 23 is a flowchart showing operations of a position
estimation device shown in FIG. 22.
DESCRIPTION OF EMBODIMENTS
[0040] To achieve the above object, a position estimation device
according to a first aspect of the present invention includes: a
setting unit configured to set current position information
indicating an estimated current position of a wireless terminal; an
estimation unit configured to estimate, using receiving strengths
of signals received from plural wireless stations including at
least a mobile station, distance information indicating distances
from the plural wireless stations to the wireless terminal; a
calculation unit configured to calculate, using the distance
information and map information indicating a spatial structure, an
area in the spatial structure in which the wireless terminal
satisfies the distances indicated in the distance information, as a
possible area in the spatial structure in which the wireless
terminal is likely to be present, the spatial structure including
at least a layout of a building; and a correction unit configured
to correct the current position indicated in the current position
information to a position within the possible area when the current
position is outside the possible area.
[0041] With this configuration, using the map information and the
distance information indicating the distances from the wireless
stations increases the accuracy of the estimation of the position
of the wireless terminal without requiring addition of a special
positioning device even when there are few base stations whose
positions are known in advance.
[0042] Thus, it is possible to provide a position estimation device
which increases the accuracy of the position estimation without
requiring addition of a special positioning device when there are
few base stations whose positions are known in advance.
[0043] Here, for example, in the first aspect, a position
estimation device according to a second aspect may be in the
wireless terminal, for example.
[0044] Furthermore, for example, in the first or second aspect, a
position estimation device according to a third aspect may be a
position estimation device wherein the spatial structure indicated
in the map information includes the layout of the building and a
position, in the building, of an obstacle which attenuates a
signal, and when the obstacle is present in the spatial structure
in a first distance indicated in the distance information, the
calculation unit is configured to calculate the possible area using
a second distance which is obtained by correcting the first
distance according to the obstacle.
[0045] With this configuration, the distance information is
corrected according to the obstacle that attenuates the wireless
signal, and thus it is possible to increase the accuracy of the
estimation of the position of the wireless terminal.
[0046] Furthermore, for example, in the first to third aspect, a
position estimation device according to a fourth aspect may be a
position estimation device further including an instruction unit
configured to instruct wireless stations which, among the plural
wireless stations, belong to a same network to change a
communication mode, wherein the estimation unit is configured to
measure receiving strengths of signals transmitted by the wireless
stations which have changed the communication mode in response to
the instruction, and estimate the distance information using the
measured receiving strengths.
[0047] With this configuration, it is possible to estimate the
distance information indicating the distances from the wireless
stations present in the same network and to use the distance
information for the position estimation.
[0048] Furthermore, for example, in the first to fourth aspect, a
position estimation device according to a fifth aspect may be a
position estimation device further including, for example, an
obtaining unit configured to communicate with each of the plural
wireless stations and obtain wireless station information held by
each of the plural wireless stations, wherein the calculation unit
is configured to calculate the possible area using the map
information, the distance information, and the wireless station
information.
[0049] Here, for example, in the fifth aspect, a position
estimation device according to a sixth aspect may be a position
estimation device wherein the wireless stations include a mobile
station and a fixed station, and the wireless station information,
when held by one of the wireless stations which is a fixed station,
includes position information indicating a position of the fixed
station.
[0050] With this configuration, the possible area is calculated
using the position information on the fixed station which belongs
to the same network, and the position estimation is performed using
the calculated possible area, and thus it is possible to increase
the accuracy of the estimation of the position of the wireless
terminal.
[0051] Furthermore, for example, in the fifth or sixth aspect, a
position estimation device according to a seventh aspect may be a
position estimation device wherein the wireless station information
includes distance information indicating a distance between one of
the wireless stations which holds the wireless station information
and a different one of the wireless stations.
[0052] With this configuration, it is possible to calculate a
relative positional relationship between the wireless stations that
belong to the same network using the distance information which is
held by each wireless station and indicates the distance between
the wireless station and another wireless station, and to calculate
the possible area using the relative positional relationship
between the wireless stations that belong to the same network. As a
result, it is possible to increase the accuracy of the estimation
of the position of the wireless terminal performed using the
calculated possible area.
[0053] Furthermore, for example, in the fifth to seventh aspect, a
position estimation device according to an eighth aspect may be a
position estimation device wherein, for example, the wireless
station information includes a transmitting strength of a signal
transmitted by the wireless station holding the wireless station
information, and the estimation unit is configured to estimate the
distance information using the receiving strengths and the
transmitting strength.
[0054] With this configuration, it is possible to increase the
accuracy of the estimation of the distance from the wireless
station, and this leads to an increase in the accuracy of the
estimation of the position of the wireless terminal.
[0055] Furthermore, for example, in the first to eighth aspect, a
position estimation device according to a ninth aspect may be a
position estimation device further including, for example, a
detection unit configured to detect acceleration information on the
wireless terminal and direction information on the wireless
terminal, wherein the setting unit is configured to set, as the
current position information, a current position estimated by
autonomous navigation using the acceleration information and the
direction information detected by the detection unit.
[0056] Furthermore, for example, in the first to eighth aspect, a
position estimation device according to a tenth aspect may be a
position estimation device wherein, for example, the estimation
unit is configured to estimate, using a receiving strength of a
signal received from a base station included in the plural wireless
stations, distance information indicating a distance from the base
station to the wireless terminal, and the setting unit is
configured to set, as the current position information, a position
of the wireless terminal estimated using the distance information
indicating the distance from the base station to the wireless
terminal and position information on the base station.
[0057] Furthermore, for example, in the first to eighth aspect, a
position estimation device according to an eleventh aspect may be a
position estimation device further including, for example: a
detection unit configured to detect acceleration information on the
wireless terminal and direction information on the wireless
terminal; and an autonomous navigation position estimation unit
configured to estimate the current position of the wireless
terminal by autonomous navigation using the acceleration
information and the direction information detected by the detection
unit, wherein the setting unit is configured to set, as the current
position information, the current position estimated by the
autonomous navigation position estimation unit.
[0058] Furthermore, for example, in the eleventh aspect, a position
estimation device according to a twelfth aspect may be a position
estimation device further including a determination unit configured
to determine whether or not the current position information set by
the setting unit needs to be corrected, based on current position
accuracy indicating accuracy of the current position estimated by
the autonomous navigation position estimation unit, wherein the
determination unit is configured to determine that the current
position information needs to be corrected when the current
position accuracy is lower than or equal to a threshold, and the
calculation unit is configured to calculate the possible area only
when the determination unit determines that the current position
information needs to be corrected.
[0059] Furthermore, for example, in the twelfth aspect, a position
estimation device according to a thirteenth aspect may be a
position estimation device wherein the current position accuracy
has a value which decreases with increase in interval between a
first time and a second time to indicate a decrease in the accuracy
of the current position, the first time being a time at which the
current position has been estimated by the autonomous navigation
position estimation unit and the second time being a time at which
a previous current position before the current position has been
estimated by the autonomous navigation position estimation
unit.
[0060] It is to be noted that these general and specific aspects
may be realized using a system, a method, an integrated circuit, a
computer program, or a computer-readable recording medium such as a
CD-ROM, or any combination of systems, methods, integrated
circuits, computer programs, or recording media.
[0061] Hereinafter, a position estimation device according to an
aspect of the present invention will be specifically described
using the drawings. It is to be noted that the embodiment described
below shows one specific example of the present invention. The
numerical values, shapes, materials, structural elements, the
arrangement and connection of the structural elements, steps, the
processing order of the steps etc., shown in the following
embodiment are mere examples, and are therefore not intended to
limit the present invention. Furthermore, among the structural
elements in the following embodiment, structural elements not
recited in any of the independent claims representing the most
generic concepts are described as arbitrary structural
elements.
Embodiment
[0062] Hereinafter, an embodiment of the present invention will be
described using the drawings. A position estimation device 100
according to an aspect of the present invention, for example, is
included in a wireless terminal such as a mobile phone, and has a
function to estimate a current position of the wireless terminal
(hereinafter referred to as "target terminal").
<1. Configuration>
[0063] FIG. 1 is a block diagram showing a configuration of the
position estimation device 100 according to Embodiment 1. As shown
in FIG. 1, the position estimation device 100 includes a sensor
unit 101, a wireless processing unit 105, a control unit 106, and a
storage unit 119. The sensor unit 101 includes an acceleration
sensor 102, an angular velocity sensor 103, and a geomagnetic
sensor 104. The control unit 106 includes a terminal information
calculation unit 107, an autonomous navigation position estimation
unit 110, a wireless strength measurement unit 111, a distance
estimation unit 112, an RSSI position estimation unit 113, a
provisional position setting unit 114, a communication mode change
instruction unit 115, a transmission and reception control unit
116, a possible area calculation unit 117, and a correction unit
118. The terminal information calculation unit 107 includes an
orientation change amount calculation unit 108 and a terminal
movement amount calculation unit 109.
[0064] The sensor unit 101 is an example of a detection unit, and
detects acceleration information on the target terminal and
direction information on the target terminal, for example.
Hereinafter, the acceleration sensor 102, the angular velocity
sensor 103, and the geomagnetic sensor 104 included in the sensor
unit 101 will be described.
[0065] The acceleration sensor 102 detects the acceleration of the
target terminal in three axial directions, converts the detected
acceleration into an electrical signal, and outputs the electrical
signal to the terminal information calculation unit 107 as
acceleration information.
[0066] The angular velocity sensor 103 detects the angular velocity
of the target terminal in the three axial directions, converts the
detected angular velocity into an electrical signal, and outputs
the electrical signal to the terminal information calculation unit
107 as angular velocity information.
[0067] The geomagnetic sensor 104 detects the geomagnetism in the
three axial directions, converts the detected geomagnetism into an
electrical signal, and outputs the electrical signal to the
terminal information calculation unit 107 as geomagnetism
information.
[0068] The wireless processing unit 105 includes an antenna or the
like, and has a function to transmit and receive a wireless signal
to communicate with other wireless stations. Here, wireless
stations refer to devices with a function to wirelessly communicate
with other wireless stations. Examples of the wireless stations
include a base station such as a master station of a mobile phone
and a wireless LAN access point, a mobile station such, as a mobile
phone and a PHS, and a fixed station which is fixed in position
such as a television receiver with a wireless function.
[0069] In more detail, the wireless station is a generic name for
wireless equipment and those who operate wireless equipment, and
does not include what is intended for reception only. The present
embodiment will be described assuming that the wireless stations
include a mobile station, a fixed station, and a base station, and
transmit at least a wireless signal. Furthermore, the present
embodiment will be described assuming that the mobile station is a
mobile phone or a PHS, for example, whose exact position is
unknown. Moreover, the present embodiment will be described
assuming that the exact position of the base station is known. It
is to be noted that the fixed station is a station which is fixed
in position, such as a television receiver, and whose position is
not necessarily known; however, the present embodiment will be
described assuming that the position of the fixed station, such as
a television receiver with a wireless function, is known.
[0070] The orientation change amount calculation unit 108
calculates, based on the angular velocity information received from
the sensor unit 101, an orientation change amount that is an amount
of change in orientation from the previous position estimation, and
outputs the calculated orientation change amount to the autonomous
navigation position estimation unit 110. In the present embodiment,
the orientation change amount is an amount of change in the angles
of the target terminal which are detected in the three axial
directions by the angular velocity sensor, and is calculated by
integrating the angular velocity information.
[0071] The terminal movement amount calculation unit 109
calculates, based on the acceleration information and the
geomagnetism information received from the sensor unit 101, a
movement amount of the target terminal that is an amount of
movement of the target terminal from the previous position
estimation, and outputs the calculated movement amount of the
target terminal to the autonomous navigation position estimation
unit 110. In the present embodiment, used as the movement amount
from the previous position estimation is a distance calculated by
integrating twice the acceleration in the X-axis direction
(east-west direction), the acceleration in the Y-axis direction
(south-north direction), and the acceleration in the Z-axis
direction (height) in the geocentric orthogonal coordinate system,
which are calculated using the acceleration information and the
geomagnetism information.
[0072] The autonomous navigation position estimation unit 110
includes a clock unit not shown in FIG. 1, and has (1) a function
to measure a time period which has elapsed from the previous
position estimation, (2) a function to add, to the position
information obtained from the previous position estimation, the
movement amount of the target terminal received from the terminal
information calculation unit 107, to calculate autonomous position
information indicating a position estimated by autonomous
navigation, and (3) a function to calculate autonomous position
accuracy information indicating the accuracy of the above
provisional position, using the orientation change amount and the
movement amount of the target terminal that are received from the
terminal information calculation unit 107 and the above-mentioned
elapsed time period. The autonomous navigation position estimation
unit 110 outputs the calculated autonomous navigation position
information and autonomous navigation accuracy information to the
provisional position setting unit 114.
[0073] In such a manner, the autonomous navigation position
estimation unit 110 estimates the current position of the target
terminal by autonomous navigation using the acceleration
information and the direction information that are detected by the
sensor unit 101.
[0074] Here, the autonomous navigation accuracy information will be
described. The input from the sensor unit contains a certain amount
of error. In general, the more rapid the change is in the values
detected (acceleration, angular velocity, and geomagnetic
direction), the larger the error is. Furthermore, the error is
generally accumulated with time.
[0075] In view of the above problem, the autonomous navigation
position estimation unit 110 calculates, as the autonomous
navigation accuracy information, a value which decreases with
increase in each of the values of the orientation change amount of
the target terminal, the movement amount of the target terminal,
and the time period which has elapsed from the previous position
estimation. In the present embodiment, the autonomous navigation
position estimation unit 110 calculates, as the autonomous
navigation accuracy information, (i) a value obtained by
subtracting from 100 a quotient obtained by dividing the total
three-axial orientation change amount of the target terminal in the
directions by a predetermined threshold Tangle [rad] (e.g., n/18
[rad]), (ii) a value obtained by subtracting from 100 a quotient
obtained by dividing the total three-axial movement amount of the
target terminal by a predetermined threshold Tdistance [m] (e.g.,
100 [mm]), and (iii) a value obtained by subtracting from 100 a
quotient obtained by dividing the time period which has elapsed
from the previous measurement by a predetermined threshold Ttime
[s] (e.g., 100 [ms]), for example.
[0076] The wireless strength measurement unit 111 measures for each
wireless station the receiving field strength of the signal
received by the wireless processing unit 105. The wireless strength
measurement unit 111 outputs the measured receiving field strength
to the distance estimation unit 112 as receiving strength
information associated with a wireless station ID which identifies
a corresponding wireless station.
[0077] The distance estimation unit 112 is an example of an
estimation unit, and estimates, using the receiving strengths of
signals received from wireless stations including at least a mobile
station, distance information indicating distances from the
wireless stations to the target terminal, for example.
[0078] More specifically, the distance estimation unit 112
calculates an estimated distance to each wireless station and its
accuracy using the receiving strength information received from the
wireless strength measurement unit 111, and outputs each estimated
distance and its accuracy associated with a wireless station ID to
the RSSI position estimation unit 113 and the possible area
calculation unit 117 as estimated distance information and distance
accuracy information.
[0079] Here, when the storage unit 119 stores transmission output
of the wireless station targeted for the distance estimation, the
distance estimation unit 112 calculates the estimated distance
information and the distance accuracy information using the
transmission output.
[0080] The transmission output of the base station among the
wireless stations is stored in advance in the storage unit 119
together with data which is related to the base station and is to
be used in processing described later. FIG. 2 is an example of base
station management information 200. The base station management
information 200 includes a set of base station ID records, and each
base station ID record includes items of transmission output and
position information. Here, each base station ID is ID information
uniquely identifying a base station. The transmission output
indicates the transmission power of radio waves of each base
station, and the position information indicates the coordinates
(latitude, longitude, and height) of each base station according to
the geocentric orthogonal coordinate system.
[0081] Furthermore, the distance estimation unit 112 also
calculates the estimated distance information and the distance
accuracy information using the transmission output received from
the transmission and reception control unit 116, when the distance
estimation unit 112 has been able to obtain, through communication
with another wireless station, the transmission output of the
wireless station targeted for the distance estimation.
[0082] Here, the above-mentioned distance accuracy information will
be described. FIG. 3 is a diagram showing a relationship between
wireless receiving field strength and distance. As shown in FIG. 3,
the receiving field strength changes more significantly with
decrease in the distance between the wireless station which has
transmitted a signal and the wireless station which has received
the signal. Thus, the greater the receiving field strength is, the
more accurate the estimated distance information is. Accordingly,
the distance estimation unit 112 calculates the distance accuracy
information which increases in value with increase in the receiving
strength.
[0083] In the above-described manner, the distance estimation unit
112 calculates the distance accuracy information and the estimated
distance information according to the receiving strength.
[0084] FIG. 4 is an example of the estimated distance information
and the distance accuracy information estimated and calculated by
the distance estimation unit 112. FIG. 4 shows that the estimated
distance information on wireless stations "AP-1", "Mobile-2", and
"TV-1" are "3 m", "9 m", and "5 m", respectively, and their
distance accuracy are "90", "60", and "80", respectively. In other
words, when the receiving strength is higher, the distance
estimation unit 112 estimates a closer distance as the distance
information and calculates higher accuracy as the distance
accuracy.
[0085] Referring back to FIG. 1, the following continues with the
description of each structural element.
[0086] Based on (i) the estimated distance information indicating
the distances from the base stations and the distance accuracy
information indicating the accuracy of that estimated distance
information among the estimated distance information and the
distance accuracy information received from the distance estimation
unit 112 and (ii) the position information on the base stations
stored in the storage unit 119, the RSSI position estimation unit
113 estimates RSSI position information indicating a position
estimated based on the receiving field strength of the target
terminal and calculates RSSI accuracy information indicating the
accuracy of the RSSI position information, and outputs the RSSI
position information and the RSSI accuracy information to the
provisional position setting unit 114. The RSSI accuracy
information in the present embodiment is, for example, the average
value of the distance accuracy information of the estimated
distance information used in estimating the RSSI position
information.
[0087] Here, the RSSI position information estimated by the RSSI
position estimation unit 113 will be described. For example,
suppose that the RSSI position estimation unit 113 has received
from the distance estimation unit 112 the distance information
"L1", "L2", and "L3" indicating the distances from three base
stations "AP-1", "AP-2", and "AP-3", respectively, and that the
respective position information (X1, Y1, X1), (X2, Y2, Z2), and
(X3, Y3, Z3) on the base stations "AP-1", "AP-2", and "AP-3" are
stored in the storage unit 119. The RSSI position estimation unit
113 estimates, as the RSSI position information, intersections of
the spherical surface of a circle having a radius L1 centering on
the base station "AP-1"
((X-X1).sup.2+(Y-Y1).sup.2+(Z-Z1).sup.2=L1.sup.2), the spherical
surface of a circle having a radius L2 centering on the base
station "AP-2" ((X-X2).sup.2+(Y-Y2).sup.2+(Z-Z2).sup.2=L2.sup.2),
and the spherical surface of a circle having a radius L3 centering
on the base station "AP-3"
((X-X3).sup.2+(Y-Y3).sup.2+(Z-Z3).sup.2=L3.sup.2). The above
equations give two points as the RSSI position information;
however, by, for example, using fourth distance information which
fixes the Z-axis, the RSSI position information will be determined
as one point.
[0088] The provisional position setting unit 114 is an example of a
setting unit, and sets current position information indicating an
estimated current position of the target terminal, for example.
Here, for example, the provisional position setting unit 114 sets,
as the current position information, the position information which
is estimated by autonomous navigation using the acceleration
information and the direction information on the target terminal
that are detected by the sensor unit 101. Furthermore, for example,
the provisional position setting unit 114 sets, as the current
position information, the position of the target terminal estimated
using the distance information indicating the distance from a base
station to the target terminal and the position information on the
base station. It is to be noted that in the present embodiment, the
current position information indicating the estimated current
position of the target terminal is also referred to as provisional
position information indicating a provisional position (provisional
current position) of the target terminal.
[0089] More specifically, the provisional position setting unit 114
calculates the provisional position information indicating the
provisional position of the target terminal and provisional
position accuracy information indicating the accuracy of the
provisional position information based on the autonomous navigation
position information and the autonomous navigation accuracy
information received from the autonomous navigation position
estimation unit 110 and the RSSI position information and the RSSI
accuracy information received from the RSSI position estimation
unit 113. The provisional position setting unit 114 outputs the
calculated provisional position information and provisional
position accuracy information to the correction unit 118. For
example, the provisional position setting unit 114 calculates, as
the provisional position information, a weighted average of the
autonomous navigation position information and the RSSI position
information using the autonomous navigation accuracy information
and the RSSI accuracy information as weights, and calculates, as
the provisional position accuracy information, an average value of
the autonomous navigation accuracy information and the RSSI
accuracy information.
[0090] It is to be noted that when the RSSI position estimation
unit 113 cannot estimate the RSSI position information, the
provisional position setting unit 114 outputs the autonomous
navigation position information and the autonomous navigation
accuracy information to the correction unit 118 as the provisional
position information and the provisional position accuracy
information.
[0091] FIG. 5 is a diagram showing map information and an example
of placement of wireless stations according to Embodiment 1. Here,
the map information is information indicating a spatial structure
including at least a layout of a building. It is to be noted that
the spatial structure indicated in the map information may include
a layout of a building and the position, in the building, of an
obstacle that attenuates a signal.
[0092] FIG. 5 shows map information 500 indicating the structure of
a private space such as home and an example of placement of
wireless stations in the map information. In general, there are
plural wireless stations in a private space such as home, and the
wireless terminals belong to the same network.
[0093] Referring back to FIG. 1, the following continues with the
description.
[0094] The communication mode change instruction unit 115 is an
example of an instruction unit, and instructs wireless stations
which, among the plural wireless stations, belong to the same
network to change the communication mode, for example. In that
case, the distance estimation unit 112 measures the receiving
strengths of signals transmitted by the wireless stations that have
changed the communication mode in response to the above
instruction, and estimates the distance information using the
measured receiving strengths.
[0095] More specifically, the communication mode change instruction
unit 115 instructs the wireless stations that belong to the same
network to temporarily change the communication mode. The
communication mode change instruction unit 115, for example,
instructs a mobile station or a fixed station to (i) behave like a
wireless access point as in the tethering mode or the like, or (ii)
be in a similar state in the ad hoc mode or the like. Receiving the
signals transmitted by the wireless stations in response to the
above instruction enables the position estimation device 100 to
calculate the estimated distance information even for the wireless
stations other than the base station.
[0096] It is to be noted that the communication mode change
instruction may instruct the wireless stations to (i) make an
instant response (transmit information held by the wireless
stations before changing the communication mode) or (ii) make a
response after measurement is completed (transmit measured distance
information and distance accuracy information when the wireless
stations have a distance measuring function). In the case of the
response after the measurement is completed, the target terminal
can increase the accuracy of the distance information by using
bidirectional distance information obtained by receiving the
distance information indicating the distances from the wireless
stations to the target terminal measured by the respective wireless
stations. Furthermore, receiving the distance information which
indicates the distances from the other wireless stations measured
by the respective wireless stations enables the target terminal to
obtain the distance information indicating relative distances
between three wireless stations including the target terminal.
[0097] The transmission and reception control unit 116 is an
example of an obtaining unit, and communicates with each of the
plural wireless stations and obtains wireless station information
held by each of the plural wireless stations, for example. Here,
the wireless station information, when held by one of the wireless
stations which is a fixed station, for example, includes position
information indicating the position of the fixed station.
Furthermore, the wireless station information may include distance
information indicating the distance between one of the wireless
stations which holds the wireless station information and a
different one of the wireless stations. Moreover, the wireless
station information may include a transmitting strength of a signal
transmitted by the wireless station holding the wireless station
information.
[0098] More specifically, the transmission and reception control
unit 116 communicates with the wireless stations that belong to the
same network, and when each wireless station holds its transmission
output or position information, obtains that transmission output or
the position information. FIG. 6 is a specific example of wireless
station information 600 in which the wireless station IDs and the
obtained transmission output and position information are
associated with each other. FIG. 6 shows that the transmission
output of the wireless station "Mobile-2" and the position
information on the wireless station "TV-1" have been obtained.
[0099] Furthermore, when the wireless stations that belong to the
same network have, like the target terminal, a function to estimate
the distances to the other wireless stations and hold the estimated
distance information and the distance accuracy information, the
transmission and reception control unit 116 obtains that estimated
distance information and distance accuracy information. FIG. 7 is a
specific example of other wireless station information 700
indicating the estimated distance information and the distance
accuracy information held by the wireless stations. FIG. 7 shows
that the wireless station "Mobile-2" holds the estimated distance
information and the distance accuracy information on the wireless
station "TV-1".
[0100] Referring back to FIG. 1, the following continues with the
description. The transmission and reception control unit 116
outputs the obtained wireless station information 600 and other
wireless station information 700 to the distance estimation unit
112 and the possible area calculation unit 117.
[0101] Next, the possible area calculation unit 117 will be
described.
[0102] The possible area calculation unit 117 is an example of a
calculation unit and calculates, using the map information and the
distance information, an area in the spatial structure in which the
target terminal satisfies the distances indicated in the distance
information, as a possible area in the spatial structure indicated
in the map information, in which the target terminal is likely to
be present, for example.
[0103] More specifically, the possible area calculation unit 117
calculates, based on the estimated distance information received
from the distance estimation unit 112, a possible area indicating
an area in the space indicated in the map information, in which the
target terminal is likely to be present, and outputs the possible
area to the correction unit.
[0104] Here, an example of the map information will be described
using FIG. 5.
[0105] As shown in FIG. 5, the map information includes the
position of an obstacle (e.g., wall) which attenuates the signal
transmitted by each wireless station. With the map information as
shown in FIG. 5, the possible area calculation unit 117 calculates,
as the possible area, an area in which the both ends of a line
segment indicated by the estimated distance information are likely
to be present.
[0106] Hereinafter, the method of calculating the possible area
will be described in detail using the drawings. In the description,
the target terminal targeted for the position estimation is shown
with a circle as the wireless station ID "Mobile-1". Furthermore,
the other wireless stations used in calculating the possible area
are shown with triangles as the wireless station IDs "Mobile-2",
"Mobile-3", and "TV-1".
[0107] FIG. 8A and FIG. 8B are diagrams for describing the method
of calculating the possible area when no obstacle is present on the
map indicated in the map information. Here, a map 800A shown in
FIG. 8A and a map 800B shown in FIG. 8B are spatial structures
indicated in the map information, and each shows a layout of the
same room in which no obstacle such as a wall is present.
[0108] First, as shown in FIG. 8A, the possible area calculation
unit 117 fixes the wireless station "Mobile-2" at the bottom-left
(south-west) corner among the four corners of the map, and measures
the trajectory of the target terminal "Mobile-1" which is located
apart by the distance indicated in the estimated distance
information. The map 800A can be partitioned into two areas by the
trajectory of the target terminal "Mobile-1". Among the two areas,
the area which does not include the map's bottom-left (south-west)
corner at which the wireless station "Mobile-2" is fixed is (1) the
possible area of the target terminal "Mobile-1" when the target
terminal "Mobile-1" is positioned above (north of) and right to
(east of) the wireless station "Mobile-2".
[0109] The possible area calculation unit 117 fixes the wireless
station "Mobile-2" at the bottom-right (south-east) corner, the
upper-left (north-west) corner, and the upper-right (north-east)
corner among the four corners of the map 800A, and performs the
same processing to respectively calculate (2) the possible area of
the target terminal "Mobile-1" when the target terminal "Mobile-1"
is positioned above (north of) and left to (east of) the wireless
station "Mobile-2", (3) the possible area of the target terminal
"Mobile-1" when the target terminal "Mobile-1" is positioned below
(south of) and right to (east of) the wireless station "Mobile-2",
and (4) the possible area of the target terminal "Mobile-1" when
the target terminal "Mobile-1" is positioned below (south of) and
left to (west of) the wireless station "Mobile-2".
[0110] The possible area calculation unit 117 obtains a union of
the calculated four possible areas to calculate the possible area
of the target terminal "Mobile-1" when no obstacle is present on
the map 800B indicated in the map information. FIG. 8B shows an
example of the result of calculation of the possible area of the
target terminal "Mobile-1".
[0111] In such a manner, the possible area calculation unit 117
calculates, as the possible area, a geometric area which can
maintain, on the map 800B, the distance between the target terminal
"Mobile-1" and the wireless station "Mobile-2".
[0112] Next, the following describes the case where an obstacle is
present on the map.
[0113] As previously described, the map information in some cases
includes an obstacle which attenuates a wireless signal. When the
obstacle is present between, for example, the target terminal
"Mobile-1" and the wireless station "Mobile-2" at the time of the
calculation of the possible area, the possible area calculation
unit 117 calculates the possible area using corrected distance
information obtained by correcting the estimated distance
information according to the type and number of obstacles.
[0114] More specifically, when an obstacle is present in a first
distance indicated in the distance information in the spatial
structure indicated in the map information, the possible area
calculation unit 117 calculates the possible area using a second
distance obtained by correcting the first distance according to the
obstacle. This will be specifically described below.
[0115] FIG. 9 is an example of a table 900 of types of obstacles
and correction scaling factors. When a "wall (thin)" is present
between the target terminal "Mobile-1" and the wireless station
"Mobile-2", for example, the possible area calculation unit 117
calculates the possible area using the corrected distance
information obtained by multiplying the estimated distance
information by a correction scaling factor 0.9. Furthermore, when
two obstacles, a "wall (thin)" and a "wall (thick)", are present
between the target terminal "Mobile-1" and the wireless station
"Mobile-2", the possible area calculation unit 117 calculates the
possible area using the corrected distance information obtained by
multiplying the estimated distance information by a correction
scaling factor 0.9.times.0.8=0.72.
[0116] FIG. 10A and FIG. 10B are diagrams for describing the method
of calculating the possible area when an obstacle is present on the
map shown in the map information. Here, a map 1000A shown in FIG.
10A and a map 1000B shown in FIG. 10B are spatial structures
indicated in the map information and each shows a layout of the
same room in which an obstacle such as a wall is present.
[0117] First, as shown in FIG. 10A, the possible area calculation
unit 117 fixes the wireless station "Mobile-2" at the bottom-left
(south-west) corner among the four corners of the map 1000A, and
measures the trajectory of the target terminal "Mobile-1". In doing
so, as the distance between the target terminal "Mobile-1" and the
wireless station "Mobile-2", the estimated distance information is
used when no obstacle is present in between, and the corrected
distance information obtained by correcting the estimated distance
information according to the type and number of obstacles is used
when an obstacle is present in between. The discontinuous points
generated by the use of the two types of distance information are
connected by a straight line which is used as the trajectory of the
target terminal "Mobile-1".
[0118] The map 1000A can be partitioned into two areas by the
trajectory of the target terminal "Mobile-1". Among the two areas,
the area which does not include the map's bottom-left (south-west)
corner at which the wireless station "Mobile-2" is fixed is (1) the
possible area of the target terminal "Mobile-1" when the target
terminal "Mobile-1" is positioned above (north of) and right to
(east of) the wireless station "Mobile-2".
[0119] The possible area calculation unit 117 fixes the wireless
station "Mobile-2" at the bottom-right (south-east) corner, the
upper-left (north-west) corner, and the upper-right (north-east)
corner among the four corners of the map 1000A, and performs the
same processing to respectively calculate (2) the possible area of
the target terminal "Mobile-1" when the target terminal "Mobile-1"
is positioned above (north of) and left to (east of) the wireless
station "Mobile-2", (3) the possible area of the target terminal
"Mobile-1" when the target terminal "Mobile-1" is positioned below
(south of) and right to (east of) the wireless station "Mobile-2",
and (4) the possible area of the target terminal "Mobile-1" when
the target terminal "Mobile-1" is positioned below (south of) and
left to (west of) the wireless station "Mobile-2".
[0120] The possible area calculation unit 117 obtains a union of
the calculated four possible areas to calculate the possible area
of the target terminal "Mobile-1" when an obstacle is present on
the map 1000B indicated in the map information. FIG. 10B shows an
example of the result of calculation of the possible area of the
target terminal "Mobile-1".
[0121] It is to be noted that when the transmission and reception
control unit 116 obtains the position information on a wireless
station among the pieces of information included in the wireless
station information 600 an example of which is shown in FIG. 6, the
possible area calculation unit 117 calculates the possible area
using the position information on the wireless station.
[0122] FIG. 11 is a diagram for describing the method of
calculating the possible area using the position information on a
wireless station. When the position information on the wireless
station "TV-1" is obtained, the target terminal "Mobile-1" is
present on the circumference of a circle having the estimated
distance information as the radius centering on the wireless
station "TV-1". With an error in the distance estimation taken into
account, a doughnut-shaped area having a width which is
proportional to the distance accuracy information received from the
distance estimation unit 112 is determined as the possible area of
the target terminal.
[0123] Here, when the transmission and reception control unit 116
obtains the other wireless station information 700 an example of
which is shown in FIG. 7, the possible area calculation unit 117
calculates the possible area using the other wireless station
information 700. For example, suppose that the estimated distance
information indicating the distance between the wireless stations
"Mobile-2" and "Mobile-3" has been received from the distance
estimation unit 112 and that the estimated distance information L7
indicating the distance between the wireless stations "Mobile-2"
and "Mobile-3" has been received from the transmission and
reception control unit 116. In this case, a triangle showing
relative positions of the target terminal "Mobile-1", the wireless
station "Mobile-2", and the wireless station "Mobile-3" can be
calculated using three pieces of distance information. When this
triangle moves on the map, one of the triangle vertices which
indicates the target terminal "Mobile-1" draws a trajectory which
shows the possible area of the target terminal "Mobile-1".
[0124] FIG. 12A to FIG. 12C, FIG. 13A, and FIG. 13B are diagrams
for describing the method of calculating the possible area using
the other wireless station information 700. The following first
describes the case where the triangle vertices indicate, clockwise,
the target terminal "Mobile-1", the wireless station "Mobile-2",
and the wireless station "Mobile-3". Here, a map 1200A shown in
FIG. 12A, a map 1200B shown in FIG. 12B, and a map 1200C shown in
FIG. 12C are spatial structures indicated in the map information,
and each shows a layout of the same room in which no obstacle such
as a wall is present.
[0125] As shown in FIG. 12A, the possible area calculation unit 117
fixes the wireless station "Mobile-2" at the bottom-left
(south-west) corner among the four corners of the map 1200A, and
measures the trajectory of the target terminal "Mobile-1" which is
located apart by the distance indicated in the estimated distance
information L2. Furthermore, the possible area calculation unit 117
fixes the wireless station "Mobile-3" at the bottom-left
(south-west) corner among the four corners of the map 1200A, and
measures the trajectory of the target terminal "Mobile-1".
[0126] Next, as shown in FIG. 12B, the possible area calculation
unit 117 measures the trajectory of the target terminal "Mobile-1"
while moving the wireless stations "Mobile-2" and "Mobile-3" along
the edges (bottom edge and left edge) of the map 1200B from the
state in which the wireless station "Mobile-2" is at the
bottom-left (south-west) corner among the four corners of the map
1200B and the wireless station "Mobile-3" is at the left (west)
edge of the map 1200B to the state in which the wireless station
"Mobile-3" is at the bottom-left (south-west) corner among the four
corners of the map 1200B and the wireless station "Mobile-2" is at
the bottom (south) edge of the map 1200B.
[0127] The trajectory shown in FIG. 12C is obtained through this
operation. Among the two areas partitioned into by this trajectory,
the area which does not include the bottom-left (south-west) corner
of the map 1200C is (1) the possible area of the target terminal
"Mobile-1" when the target terminal "Mobile-1" is positioned above
(north of) the wireless station "Mobile-2" and right to (east of)
the wireless station "Mobile-3".
[0128] The possible area calculation unit 117 performs the same
operation for the remaining four corners to calculate (2) the
possible area of the target terminal "Mobile-1" when the target
terminal "Mobile-1" is positioned right to (east of) the wireless
station "Mobile-2" and below (south of) the wireless station
"Mobile-3", (3) the possible area of the target terminal "Mobile-1"
when the target terminal "Mobile-1" is positioned below (south of)
the wireless station "Mobile-2" and left to (west of) the wireless
station "Mobile-3", and (4) the possible area of the target
terminal "Mobile-1" when the target terminal "Mobile-1" is
positioned left to (west of) the wireless station "Mobile-2" and
above (north of) the wireless station "Mobile-3".
[0129] The possible area calculation unit 117 obtains a union of
the calculated four possible areas to calculate the possible area
of the target terminal "Mobile-1" for the case where the other
wireless station information is used. A map 1200D in FIG. 13A shows
an example of the result of calculation of the possible area of the
target terminal "Mobile-1".
[0130] The possible area calculation unit 117 calculates the
possible areas also for the case where the triangle vertices
indicate, clockwise, the target terminal "Mobile-1", the wireless
station "Mobile-3", and the wireless station "Mobile-2", and
obtains a union of the calculated possible areas and the possible
area shown in the map 1200D in FIG. 13A to calculate the possible
area shown in a map 1200E in FIG. 13B.
[0131] In such a manner, the possible area calculation unit 117
calculates, as the possible area, a geometric area which can
maintain (satisfy), on the map 1200E, the distance between the
target terminal "Mobile-1" and the wireless station "Mobile-2", the
distance between the target terminal "Mobile-1" and the wireless
station "Mobile-3", the distance between the wireless station
"Mobile-2" and the wireless station "Mobile-3".
[0132] The possible area calculated in this manner is determined as
the possible area of the target terminal "Mobile-1" for the case
where the other wireless station information is used.
[0133] The possible area calculation unit 117 obtains a product set
of the plural possible areas calculated based on the received
estimated distance information, wireless station information, and
other wireless station information, and outputs the product set to
the correction unit 118.
[0134] Next, FIG. 14 to FIG. 17 show an example of the calculation
of the possible area in the map information and in the example of
the placement of the wireless terminals shown in FIG. 5.
[0135] FIG. 14 shows an example of the possible area calculated on
a map 500A using the estimated distance information indicating the
distance between the target terminal "Mobile-1" and the wireless
station "Mobile-2". FIG. 15 shows an example of the possible area
calculated on a map 500B using the estimated distance information
indicating the distance between the target terminal "Mobile-1" and
the wireless station "AP-1" and the base station management
information stored in the storage unit 119. FIG. 16 shows an
example of the possible area calculated on a map 500C using the
estimated distance information indicating the distance between the
target terminal "Mobile-1" and the wireless station "TV-1" and the
wireless station information obtained from the wireless station
"TV-1".
[0136] The possible area calculation unit 117, for example,
calculates these three possible areas and obtains a product set,
and outputs the resulting possible area calculated on a map 500D
shown in FIG. 17 to the correction unit 118.
[0137] Referring back to FIG. 1, the following continues with the
description of the configuration of the position estimation device
100.
[0138] When the current position (provisional position) indicated
in the current position information (provisional position
information) is outside the possible area, the correction unit 118
corrects the current position to a position within the possible
area. Specifically, the correction unit 118 corrects the
provisional position information received from the provisional
position setting unit, based on the possible area received from the
possible area calculation unit 117.
[0139] More specifically, the correction unit 118 determines
whether the coordinates indicated in the provisional position
information are within or outside the possible area, and when the
coordinates are outside the possible area, corrects the current
position to a position, within the possible area, which is closest
to the coordinates indicated in the provisional position
information. In doing so, when there are plural positions within
the possible area which are closest to the coordinates indicated in
the provisional position information, the correction unit 118
corrects the current position indicated in the provisional position
information to a position randomly selected from among the plural
positions, for example. It is to be noted that when there are
plural positions within the possible area which are closest to the
coordinates indicated in the provisional position information, a
position may be selected according to a predetermined rule (e.g.,
select the first position clockwise from the 12 o'clock direction,
or select a position from among the plural positions which is close
to the direction of the center of gravity) other than by random
selection.
[0140] The storage unit 119 stores the map information indicating a
spatial structure including at least a layout of a building. In the
present embodiment, the storage unit 119 stores the base station
management information 200, the map information 500, and the table
900 of obstacles and correction scaling factors.
[0141] It is to be noted that the possible area calculated in the
above description is on a flat plane; however, a three-dimensional
possible area can also be calculated using the same method. More
specifically, the possible area can be calculated by measuring the
trajectories of the target terminal using eight vertices as the
center.
<2. Operations>
[0142] Next, operations of the position estimation device 100
according to the present embodiment will be described.
[0143] FIG. 18 is a flowchart showing the entire operations of the
position estimation device 100 according to the present embodiment.
As shown in FIG. 18, the operations of the position estimation
device 100 include the estimation of the autonomous navigation
position information by autonomous navigation (S1801), the
estimation of the RSSI position information using the receiving
field strength (S1802), the setting of the provisional position
information indicating a provisional position of the target
terminal (S1803), the determination as to whether or not the
provisional position information needs to be corrected (S1804), and
the correction of the provisional position information using the
possible area (S1805).
[0144] FIG. 19 is a flowchart showing the operation of estimating
the autonomous navigation position information (S1801).
[0145] As shown in FIG. 19, first, the orientation change amount
calculation unit 108 calculates an orientation change amount of the
target terminal based on the angular velocity information received
from the angular velocity sensor 103 (S1901), and the terminal
movement amount calculation unit 109 calculates a movement amount
of the target terminal based on the acceleration information
received from the acceleration sensor 102 and the geomagnetism
information received from the geomagnetic sensor 104 (S1902).
[0146] Next, the autonomous navigation position estimation unit 110
calculates the autonomous navigation position information based on
the current position information at the previous position
estimation stored in the storage unit 119 and an amount of movement
of the target terminal (S1903). The autonomous navigation position
estimation unit 110 then calculates the autonomous navigation
accuracy information based on the time period which has elapsed
from the previous position estimation and the orientation change
amount and the amount of movement of the target terminal from the
previous position estimation (S1904).
[0147] With the operations shown in FIG. 19, the position
estimation device 100 calculates the autonomous navigation position
information and the autonomous navigation accuracy information.
[0148] FIG. 20 is a flowchart showing the operation of estimating
the RSSI position information (S1802). As shown in FIG. 20, first,
the wireless strength measurement unit 111 measures the receiving
field strengths of signals transmitted by plural base stations
(S2001).
[0149] Next, the distance estimation unit 112 selects the base
stations measured by the wireless strength measurement unit 111, in
descending order of the receiving field strength (S2002).
[0150] The distance estimation unit 112 determines whether or not
the receiving field strength of the selected base station is
greater than or equal to a predetermined threshold (S2003). When
the receiving field strength is smaller than the threshold, the
process proceeds to S2005.
[0151] When the receiving field strength of the selected base
station is greater than or equal to the threshold, the distance
estimation unit 112 estimates the distance between the selected
base station and the target terminal and calculates the estimated
distance information associated with the base station ID and the
distance accuracy information indicating the accuracy of the
estimated distance information, based on the receiving strength of
the signal received from the selected base station (S2004).
[0152] It is to be noted that as shown in FIG. 3, the receiving
field strength changes more significantly with decrease in the
distance between the wireless station which has transmitted a
signal and the wireless station which has received the signal.
Thus, the lower the receiving field strength is, the less accurate
the estimated distance information is. Therefore, performing the
distance estimation only when the receiving strength is greater
than or equal to a predetermined threshold ensures the minimal
accuracy of the estimated distance information.
[0153] Referring back to FIG. 20, the following continues with the
description. The distance estimation unit 112 determines whether or
not the estimated distance information has been calculated for all
the base stations measured by the wireless strength measurement
unit 111 (S2005), and the process returns to S2002 when there is
still a base station for which the estimated distance information
has not been calculated yet.
[0154] When the estimated distance information is calculated for
all the base stations measured by the wireless strength measurement
unit 111, the RSSI position estimation unit 113 determines whether
or not the distance estimation unit 112 has calculated the
estimated distance information for three or more base stations
(S2006). When the distance estimation unit 112 has calculated the
estimated distance information for less than three base stations,
the process proceeds to S1803.
[0155] When the distance estimation unit 112 has calculated the
estimated distance information for three or more base stations, the
RSSI position estimation unit 113 calculates the RSSI position
information and the RSSI accuracy information using the position
information on the base stations stored in the storage unit 119 and
the estimated distance information (S2007).
[0156] Referring back to FIG. 18, the provisional position setting
unit 114 calculates, as the provisional position information, a
weighted average of the autonomous navigation position information
and the RSSI position information using the autonomous navigation
accuracy information and the RSSI accuracy information as weights,
and calculates, as the provisional position accuracy information,
an average value of the autonomous navigation accuracy information
and the RSSI accuracy information (S1803).
[0157] It is to be noted that when the RSSI position estimation
unit 113 cannot estimate the RSSI position information, the
autonomous navigation position information and the autonomous
navigation accuracy information are used as the provisional
position information and the provisional position accuracy
information.
[0158] The correction unit 118 determines whether or not the
provisional position accuracy information is smaller than a
predetermined threshold (S1804), and finishes the process when the
provisional position accuracy information is greater than or equal
to the threshold, determining the provisional position information
as the final result of the position estimation.
[0159] When the provisional position accuracy information is
smaller than the predetermined threshold, the position estimation
device 100 corrects the provisional position information using the
possible area (S1805).
[0160] FIG. 21 is a flowchart showing operations of correcting the
provisional position information using the possible area.
[0161] First, the communication mode change instruction unit 115
instructs the wireless stations that belong to the same network to
change the communication mode (S2101). Next, the transmission and
reception control unit 116 communicates with the wireless stations
that belong to the same network and obtains the wireless station
information and the other wireless station information (S2102).
[0162] Furthermore, the wireless strength measurement unit 111
measures the receiving field strengths of the signals transmitted
by the wireless stations that belong to the same network
(S2103).
[0163] Next, the distance estimation unit 112 selects the base
stations measured by the wireless strength measurement unit 111, in
descending order of the receiving field strength (S2104).
[0164] The distance estimation unit 112 determines whether or not
the receiving field strength of the selected base station is
greater than or equal to a predetermined threshold (S2105). When
the receiving field strength is smaller than the threshold, the
process proceeds to S2107.
[0165] When the receiving field strength of the selected base
station is greater than or equal to the threshold, the distance
estimation unit 112 estimates the distance between the selected
base station and the target terminal and calculates the estimated
distance information associated with the base station ID and the
distance accuracy information indicating the accuracy of the
estimated distance information, based on the receiving strength of
the signal received from the selected base station (S2106).
[0166] The distance estimation unit 112 determines whether or not
the estimated distance information has been calculated for all the
base stations measured by the wireless strength measurement unit
111 (S2107), and the process returns to S2104 when there is still a
base station for which the estimated distance information has not
been calculated yet.
[0167] When the estimated distance information is calculated for
all the wireless stations measured by the wireless strength
measurement unit 111, the possible area calculation unit 117
calculates the possible area based on the estimated distance
information, the wireless station information, the other wireless
station information, and the map information (S2108).
[0168] When the possible area is calculated, the correction unit
118 corrects the provisional position information using the
possible area (S2109) and finishes the process, determining the
correction result as the final result of the position estimation
(current position information).
<3. Conclusion>
[0169] The position estimation device 100 according to the present
embodiment calculates the possible area for the provisional
position information, using the map information indicating a
spatial structure and information on the wireless stations which
belong to the same network. The position estimation device 100 then
corrects the provisional position information using the possible
area.
[0170] This configuration enables accurate estimation of the
position of the target terminal using the map information and the
wireless station information on the wireless stations which belong
to the same network, even when there are few base stations and/or
when the wireless terminal is not equipped with a special
positioning device.
(Supplementary Notes)
[0171] Although only an exemplary embodiment of the position
estimation device according to an aspect of the present invention
has been described above, the present invention is not limited to
this embodiment. Those skilled in the art will readily appreciate
that various modifications may be made in this embodiment and that
other embodiments may be obtained by combining the structural
elements of different embodiments without materially departing from
the novel teachings and advantages of the present invention.
Accordingly, all such modifications and other embodiments may be
included in the scope of one or more aspects of the present
invention. The exemplified position estimation device may be
modified as below. The following describes the examples.
[0172] (1) In the above-described embodiment, the base station
management information 200 shown in FIG. 2 is stored in the storage
unit in advance; however, the present invention is not limited to
this.
[0173] For example, the base station management information 200 may
be stored in an externally-provided storage device, and the target
terminal may obtain the base station management information through
communication with the storage device as necessary.
[0174] (2) In the above-described embodiment, the movement amount
of the target terminal is calculated by integrating the
acceleration information twice; however, the method of calculating
the movement amount of the target terminal is not limited to this.
For example, the following is also possible: information on the
length of stride or the like of a user of the target terminal is
obtained in advance from the user, and the user's steps are
detected using the acceleration information, to calculate the
product of the length of stride and the steps as the movement
amount of the target terminal.
[0175] (3) In the above-described embodiment, the possible area of
the target terminal is calculated by measuring the trajectories of
the target terminal using the wireless stations other than the
target terminal as the center; however, the method of calculating
the possible area is not limited to this. For example, presuming
that the target terminal is present at particular coordinates on
the map, the particular coordinates are determined as possible
coordinates when a wireless station other than the target terminal
is likely to be present on the map based on the estimated distance
information, whereas the particular coordinates are determined as
impossible coordinates when a wireless station other than the
target terminal is not likely to be present on the map based on the
estimated distance information. All the coordinates on the map are
classified into the possible coordinates or the impossible
coordinates, and the resulting set of the possible coordinates may
be determined as the possible area.
[0176] (4) The above-described embodiment and modifications may be
combined in part.
[0177] For example, the position estimation device according to the
above embodiment is included in the target terminal; however, the
present invention is not limited to this. The position estimation
device may be included in a server such as a cloud connected with
the target terminal via a network.
[0178] (5) It is also possible to record on recording media or
distribute via various communication paths and so on a control
program including program codes which are written in machine
language or a high-level language to cause a processor of the
position estimation device and various circuits connected to the
processor to execute the distance estimation, correction, and other
processes described in the above embodiment. Examples of the
recording media include IC cards, hard disks, optical discs,
flexible disks, ROMs, and flash memories. The distributed control
program is provided for use by being stored in a memory and the
like which can be read by the processor. As the processor executes
the control program, each function described in the above
embodiment is implemented. It is to be noted that rather than by
directly executing the control program, the processor may execute
the control program through compilation or by using an
interpreter.
[0179] (6) Each functional structural element described in the
above embodiment may be realized as a circuit which executes the
function of the functional structural element or realized through
execution of a program by one or more processors.
[0180] In other words, each structural element described in the
above embodiment may be realized as dedicated hardware or realized
through execution of a software program appropriate for the
structural element. Each structural element may be realized through
reading and execution, by a program execution unit such as CPU or a
processor, of a software program recorded on a recording medium
such as a hard disk or a semiconductor memory.
[0181] Here, the software program for realizing the position
estimation device and so on according to the above embodiment is
such a program as follows: Specifically, this program, executed by
a computer, includes: setting current position information
indicating an estimated current position of a wireless terminal;
estimating, using receiving strengths of signals received from
plural wireless stations including at least a mobile station,
distance information indicating distances from the plural wireless
stations to the wireless terminal; calculating, using the distance
information and map information indicating a spatial structure, an
area in the spatial structure in which the wireless terminal
satisfies the distances indicated in the distance information, as a
possible area in the spatial structure in which the wireless
terminal is likely to be present, the spatial structure including
at least a layout of a building; and correcting the current
position indicated in the current position information to a
position within the possible area when the current position is
outside the possible area.
[0182] Furthermore, the position estimation device according to an
aspect of the present invention may be provided as a package of an
integrated circuit such as IC and LSI. This package is incorporated
into various devices for use, which allows the various devices to
perform each function described in the embodiment.
[0183] It is to be noted that each functional block such as the
distance estimation unit, each position estimation unit, the
possible area calculation unit, and the correction unit is
typically realized in the form of an LSI that is an integrated
circuit. These LSIs may be manufactured as individual chips, or
some or all of the LSIs may be integrated into one chip. Although
the name used here is LSI, it is also called IC, system LSI, super
LSI, or ultra LSI depending on the degree of integration.
Furthermore, the means for circuit integration is not limited to
the LSI, and a dedicated circuit and a general-purpose processor
are also available. It is also acceptable to use: a field
programmable gate array (FPGA) that is programmable after the LSI
has been manufactured; and a reconfigurable processor in which
connections and settings of circuit cells within the LSI are
reconfigurable. Furthermore, if circuit integration technology that
replaces LSI appears through progress in the semiconductor
technology or other derivative technology, that circuit integration
technology can be used for the integration of the functional
blocks. Adaptation and so on of biotechnology is one such
possibility.
(Supplementary Notes 2)
[0184] It is to be noted that although the position estimation
device 100 in the above description includes the sensor unit 101,
the wireless processing unit 105, the control unit 106, and the
storage unit 119, the position estimation device is not limited to
this. As shown in FIG. 22, a position estimation device 100A is
sufficient as the minimum configuration of the position estimation
device. Specifically, the position estimation device 100A including
the distance estimation unit 112, the provisional position setting
unit 114, the possible area calculation unit 117, and the
correction unit 118 is sufficient.
[0185] More specifically, the position estimation device 100A is
sufficient which includes: the provisional position setting unit
114 configured to set current position information indicating an
estimated current position of a wireless terminal; the distance
estimation unit 112 configured to estimate, using receiving
strengths of signals received from plural wireless stations
including at least a mobile station, distance information
indicating distances from the plural wireless stations to the
wireless terminal; the possible area calculation unit 117
configured to calculate, using the distance information and map
information indicating a spatial structure, an area in the spatial
structure in which the wireless terminal satisfies the distances
indicated in the distance information, as a possible area in the
spatial structure in which the wireless terminal is likely to be
present, the spatial structure including at least a layout of a
building; and the correction unit 118 configured to correct the
current position indicated in the current position information to a
position within the possible area when the current position is
outside the possible area.
[0186] With at least the position estimation device 100A, the
position of a wireless terminal can be estimated with higher
accuracy using the map information and the distance information
indicating the distances from the wireless station without
requiring addition of a special positioning device even when there
are few base stations whose positions are known in advance.
[0187] It is to be noted that an aspect of the position estimation
device 100A may be realized by a method shown in FIG. 23. More
specifically, it may be realized by a method including setting
current position information indicating an estimated current
position of a wireless terminal (S101); estimating, using receiving
strengths of signals received from plural wireless stations
including at least a mobile station, distance information
indicating distances from the plural wireless stations to the
wireless terminal (S102); calculating, using the distance
information and map information indicating a spatial structure, an
area in the spatial structure which can maintain the distances
indicated in the distance information, as a possible area in the
spatial structure in which the wireless terminal is likely to be
present, the spatial structure including at least a layout of a
building (S103); and correcting the current position indicated in
the current position information to a position within the possible
area (S105) when the current position is outside the possible area
(No in S104).
INDUSTRIAL APPLICABILITY
[0188] The position estimation device according to the present
disclosure can be used for various applications such as mobile
phones, PHSs, wristwatches, and wireless tags.
REFERENCE SIGNS LIST
[0189] 100, 100A Position estimation device [0190] 101 Sensor unit
[0191] 102 Acceleration sensor [0192] 103 Angular velocity sensor
[0193] 104 Geomagnetic sensor [0194] 105 Wireless processing unit
[0195] 106 Control unit [0196] 107 Terminal information calculation
unit [0197] 108 Orientation change amount calculation unit [0198]
109 Terminal movement amount calculation unit [0199] 110 Autonomous
navigation position estimation unit [0200] 111 Wireless strength
measurement unit [0201] 112 Distance estimation unit [0202] 113
RSSI position estimation unit [0203] 114 Provisional position
setting unit [0204] 115 Communication mode change instruction unit
[0205] 116 Transmission and reception control unit [0206] 117
Possible area calculation unit [0207] 118 Correction unit [0208]
119 Storage unit [0209] 200 Base station management information
[0210] 500 Map information [0211] 500A, 500B, 500C, 500D, 800A,
800B, 1000A, 1000B, 1200A, 1200B, 1200C, 1200D, 1200E Map [0212]
600 Wireless station information [0213] 700 Other wireless station
information
* * * * *